This invention is directed to a polymer blend containing a chlorinated polyethylene or chlorosulfonated polyethylene elastomer and certain ethylene-containing terpolymers which results in a blend having improved low temperature properties and good oil swell resistance.
Chlorinated polyethylene and chlorosulfonated polyethylene elastomers have been used for many years to make, among other things, rubber hose, oil seals, O-rings and tubing for use in environments where the product is exposed to oil and low temperatures, for example, automotive use. In such an environment the polymeric material must be resistant to swelling in oil and flexible at low temperatures. Chlorinated polyethylene and chlorosulfonated polyethylene are characterized by showing an improvement in oil resistance as the percent chlorine is increased. Unfortunately, however, an increase in the percent chlorine in the chlorinated polyolefin has a detrimental effect on the low temperature flexibility of the chlorinated polyolefin and, further, high levels of chlorine increases the glass transition temperature (Tg) of the chlorinated polyolefin. Attempts to improve the low temperature properties of the polymers while maintaining oil swell resistance have included the addition of plasticizers to the polymers. The results of such modification of the chlorinated polyolefins was less than satisfactory because the plasticizers had a tendency to migrate to the surface, were fugitive and, in addition, the incorporation of relatively large amounts of plasticizer in the polymers resulted in deterioration of the physical properties of the polymer. It has been a goal of the industry to manufacture chlorinated polyethylene or chlorosulfonated polyethylene elastomer compositions that have a relatively high chlorine content and thus are resistant to swelling when contacted with oil, and, at the same time, exhibit excellent low temperature flexibility.